Osteoarthritis (OA) is a leading cause of disability in the US affecting almost 30 million people at an annual cost of $128 billion. Initiation of OA is tid to genetic predisposition, chronic overload, or acute injury due to joint trauma. The development of OA after acute injury is particularly prevalent with more than 50% of injury developing full blown symptomatic OA 10-20 years after injury. Despite the importance of this topic and decades of research, the local mechanical events that occur in cartilage during tissue injury are still poorly understood. In this proposal we take advantage of newly developed microscopy and image analysis techniques to determine how the organization of the tissue governs its microscale response to joint loading. We build on recent results (through NIH support R21AR054867) showing that cartilage has an energy absorbing region just below its surface and hypothesize that the function of this region is to protect underlying tissue from damage by locally absorbing the strain. We also hypothesize that conditions that alter the organization of this region and alter its ability to absorb energy also compromise its ability to shield underlying tissue from injurious loads. Identifying the link between the unique mechanical properties of this region and its role in regulating the response of the tissue as a whole to mechanical injury would be a fundamental shift in our approach towards understanding the initiation of cartilage damage after joint injury. Results from these studies are critical to developing a more clinically relevan understanding of function in normal tissue, enabling more effective diagnosis and monitoring of human disease, and providing benchmarks and design input for efforts to replace or regenerate tissue.